Rotary kilns with cooler tubes



United States Patent Great Britain No. 43,332/67 ROTARY KILNS WITHCOOLER TUBES 5 Claims, 7 Drawing Figs.

Int. Cl F27!) 7/00 Field of Search 263/32, 3 2C, 52

Primary Examiner-John J. Camby Attorney-Pennie, Edmonds, Morton, Taylorand Adams ABSTRACT: A rotary kiln having a number of cylindrical coolertubes mounted in planetary fashion around the outlet end of their kilnwith their axes parallel or substantially parallel to the axis of thekiln, with the inlet end of each cooler tube being connected to anoutlet end of the rotary kiln by a supply chute. Helical conveyorflights are provided in the tubes to lift the material in each coolertube and discharge it in the form of falling curtains of materialinclined to the axis of the tube so that cooling air must pass throughcurtains before entering the kiln. The improvement is in a ring ofscoops provided at the air inlet end of each tube to produce atransverse curtain of material over that side of the tube in which theconveyor flights are moving upwards to impede the entry of incoming airinto channels formed between adjacent inclined curtains PATENI'ED nan5197s saw 1 BF 2 INVENTOR FLEMMING EDWIN JENSEN I ATTORNEYS PATENTED0521 51916 35472418 sum 2 a? 2 FIG. 3

FIG.6 $56.5 FIG.4

INVENTOR FLEMMING EDWIN JENSEN R, ww MAT ATTORNEYS ROTARY KILNS WITHCOOLER TUBES BACKGROUND OF THE INVENTION 1 Field of the Invention Thisinvention relates to that kind of rotary kiln which has a number ofcylindrical cooler tubes mounted in planetary fashion around the outletend of the kiln with their axes parallel or substantially parallel tothe axis of the kiln, the inlet end of each cooler tube being connectedto an outlet of the rotary kiln by a supply chute. The tubes may extendaway from the kiln, but more usually they extend from the outlet end ofthe kiln in the direction towards the inlet end of it.

2. Description of the Prior Art The assembly of these tubes is commonlycalled a planetary cooler and is a well-known construction widely usedin the ceramic industry, particularly for cooling cement clinker formedby burning in the rotary kiln.

The hot material leaving the rotary kiln through the communicatingchutes is cooled in the cooler tubes by air which passes through thetubes in countercurrent to the stream of hot material. The movement ofthe hot material is caused by the rotation of the kiln, with which thecooler tube is integral. In order to enable the material in the kilntomove easily along it, the kiln axis is normally slightly inclined to thehorizontal. The tubes may be parallel to the axis and extend towards theinlet of the kiln, and then the material must move uphill through them,or they may be so arranged that the material moves downhill throughthem. In any case, the movement of the material is often furthered bymeans of built-in lifters or other conveying devices, and if thematerial moves uphill through the tubes, such devices must be providedfor conveying the material through the tubes against the action ofgravity.

Commonly the lifters or conveying devices are of such a design that thematerial is lifted up inside the cooler tube and discharged again intothe stream of air flowing through the tube. If so, improved cooling ofthe material is obtained through the intimate contact achieved betweenthe air and the material.

In the cooler the air takes up heat, which is subsequently utilized inthe kiln as secondary combustion air. However, it is important that theamount of preheated air thus supplied to the kiln is correlated with thetotal amount of combustion air actually needed. The size of the coolerandthe amount of the cooling air required are therefore closely relatedto size of the kiln and the rate of production in it.

If large amounts of cooling air pass too quickly through the tubes,there will not be adequate contact between the air and the hot material,and accordingly the efficiency of the cooler will be low. To avoid thishelical conveyor flights have been provided to lift the material in eachcooler tube and discharge it in the form of falling curtains of materialinclined to the axis of the tube, so that the cooling air must passthrough curtains before entering the kiln. However, the air tends alwaysto take the easiest path through the tube, and in consequence to flowthrough the channels formed between adjacent curtains, and only to passthrough the curtains where these offer low resistance to it.

SUMMARY OF THE INVENTION tube to produce a transverse curtain ofmaterial over that side of the tube in which the conveyor flights aremoving upwards and thus to impede the entry of the incoming air intosome of the channels formed between adjacent inclined curtains.

The scoops may be separate from the conveyor flights or formed in theends of those flights. Advantageously they are equal in number, butangularly staggered in relation, to the flights.

Preferably a ring of scoops is provided at the air-outlet end of eachtube to produce a transverse curtain of material over that side of thetube in which the conveyor flights are moving downwards.

It is important that the conveyor flights should act efficiently in bothconveying the material through the tube and providing an adequate numberof curtains, and it is found that this is best done when the pitch ofthe helix of each of the flights is such that theitrace of the flight onthe wall of the tube forms an angle of between 15 and 25 with thegeneratrix of the tube. 6 I

One construction according to the invention will now be described by wayof example with reference to the accompanying diagrammatic drawings, inwhich:

DESCRIPTION OF DRAWINGS FIG. 1 is a longitudinal section through theoutlet end of a rotary kiln equipped with cooler tubes according to theinvention;

FIG. 2 is a section on the line 2-2 of FIG. 1;

FIG. 3 is an enlargement of part of FIG. 1 showing in detail alongitudinal section through a cooler tube;

FIG. 4, 5 and 6 are sections through the cooler tube taken on the lines4-4, 5-5, and 6-6 in FIG. 3, respectively; and

FIG. 7 is a diagrammatic view of a cooler tube from above, showing thedistribution of material inside the tube.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the lower end of arotary kiln 1 having a refractory lining 2 and outlet openings 3communicating through chutes 4 with twelve cooler tubes 5 arranged inplane tary fashion around the end of the rotary kiln with their axesparallel to the axis of the kiln.

The cooled material leaves each cooler tube through outlet opening 6 inthe air-inlet end of the tube, and all the openings 6 are surrounded bya stationary housing 7, the bottom of which is formed as a hopper 8 forcollecting the material. The cooled material is discharged through abottom opening 9 in the hopper 8.

The parts described so far and shown in FIGS. 1 and 2 are of theconventional construction. In the invention, each cooler tube hastrough-shaped conveyor flights 11 running helically from one end of thetube to the other as shown in FIG. 3, and at the air-inlet end a ring 12of scoops 13 is provided. These scoops have sidewalls, not shown, andconstitute a series of buckets, which pick up material from the bottomof the tube and carry it upwards as shown in FIG. 6 until the kiln, andtherefore the tube, reaches such an angular position in the course ofrotation that the material begins to fall out of the scoops 13 to form acurtain 14 extending over approximately half the cross-sectional area ofthe tube.

At the air-outlet end of the tube there is a ring 15 of scoops 16constructed likewise to engage and carry material upwards, but to holdthe material until the kiln has passed through a much greater angle ofrotation and thus to discharge it as a curtain 17 over approximately theother half of the cross sec- 1 tion of the tube from that occupied bythe curtain 14.

The conveyor flights 11 have the trough shape shown in FIG. 5, and liftthe material and in the course of rotation discharge it again in theform of curtains 18, which are inclined to the axis of the kiln. At anygiven instant these curtains 18 may be regarded as occupying theposition shown by dotted lines in FIG. 7, and channels 19 are formedbetween adjacent curtains 18. It will be seen that the curtain 14extends across the inlet ends of two comparatively long channels,leaving only a comparatively short channel for the unimpeded entry ofair. The arrows in FIG. 7 show approximately the paths taken by the airand the FIG. shows how the air is forced to pass through a number ofinclined transverse curtains. At the airnoutlet end, the presence of thecurtain l7 prevents the air from passing uninterruptedly into the kilnalong two comparatively long channels 19, the mouth of only acomparatively short channel being open to allow the unimpeded passage ofair.

The conveyor flights shown serve not merely to produce the curtains, butalso to convey the material towards the air-inlet end of the tube.

By means of the invention the heat exchange in the tube is improved, andin consequence the diameter of each tube and also the length of the tubemay be reduced in comparison with conventional planetary coolers. Thisin turn makes it possible to increase the number of cooler tubes, andaccordingly to allow a greater quantity of material to be cooled in theplanetary cooler, so that the invention is of particular value in kilnsof high output.

lclaim:

1. In a rotary kiln having cylindrical cooler tubes mounted in planetaryfashion around the outlet end of the kiln with their axes parallel orsubstantially parallel to the axis of the kiln, the inlet end of eachcooler tube being connected to an outlet of the rotary kiln by a supplychute, in which troughshaped conveyor flights run helically along theinner wall of each cooler tube to lift the material above the horizontalplane through the axis of the tube and discharge it as curtainsextending over substantially the whole width of the tube and inclined tothe axis of the tube, the improvement in combination therewithcomprising a ring of scoops provided at the air inlet end of each tubeconfigured to lift scoopfuls of material and later cause it to fallout-therefrom to produce a transverse curtain of material over that sideof the tube in which the conveyor flights are moving upwards and impedethe entry of the incoming air into some of the channels formed betweenadjacent inclined curtains.

.2. A kiln according to claim 1 in which a ring of scoops is provided atthe air-outlet end of each tube to produce a transverse curtain ofmaterial over that side of the tube in which the conveyor flights aremoving downwards.

3. A kiln according to claim 1 in which the scoops at the airoutlet endare formed in the ends of the conveyor flights.

4. A kiln according to claim 1 in which the scoops at the airinlet endare equal in number, but angularly staggered in relation, to theflights.

5. A kiln according to claim 1 in which the pitch of the helix of eachof the flights is such that the trace of the flight on the wall of thetube forms an angle of between 15 and 25 with the generatrix of thetube.

